If you try to monitor DC, be aware that all LE are encrypted. Some talkgroups on Montgomery and PG are also encrypted, but most are in the clear. At the campground, you would want to monitor College Park and Beltsville talkgroups for LE. Interestingly, PG uses "directional" antenna broadcasting, so what you hear "loud & clear" at the campground, will totally disappear about 1 mile west of that location (just after crossing into Montgomery Co -District 3 Silver Spring T/G). Also MD State Police use talkgroups on PG system. They are responsible for I-495. Enjoy your stay.